Cast nickel-base alloy



United States Patent ()fiice 3,301,670 Patented Jan. 31, 1967 3,301,670 CAST NIOKEL-BASE ALLOY. Clarence G. Bieber, Roselle Park, N.J., assignor to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware Filed Jan. 8, 1964, Ser. No. 336,458 4 Claims. (Cl. 75-171) terials which would fulfill the requirements of the engine designers. Many different alloys have been employed as blade materials over the years with varying degrees of success. In addition, numerous different methods for producing aircraft gas turbine blades have been employed, including forging and casting. Forged blades provide certain advantages, particularly from the viewpoint of excellent metallurgical soundness. However, there are practical limits imposed by commercial forging practices upon the amounts of alloying ingredients which may be included in forged nickel-base alloys. These practical limits upon the amounts of alloying ingredients which may be included in alloys intended for the production of forged blades, in turn, effectively limits the strength properties at elevated temperatures which can be achieved in forged blades. Accordingly, the art has increasingly turned to the use of cast blades so as to utilize the higher strength properties attainable with nickel-base alloys having increased amounts of alloying ingredients as compared to the amounts which may be employed in forged alloys. With the advent of improved vacuum melting and vacuum casting equipment and with strict production control in the production of investment molds for use in the casting process as well as strict control in all other aspects of vacuum melting and vacuum casting, the producers of cast blades have now been able to achieve highly consistent results in the production of cast blades and other articles manufactured from nickel-base alloys. Nevertheless, the aircraft 'gas turbine industry has continually demanded higher and higher levels of elevated a life to rupture at 1400 F. and 85,000 psi. of about 54 hours with an elongation of about 4% to about 5%. Good ductility at the temperature of about 1400 F. is highly important in gas turbine blades since the rotor portions of the blades operate at a temperature on the order of about 1400" F. and blade castings made of alloys having poor ductility at this temperature are subject to fracture in service. In addition, it is found that certain other alloys employed in the form of cast gas turbine blades tend to develop brittle acicular structures when subjected to elevated temperatures for extended periods of time, e.g., 2,000 hours. This occurrence is highly undesirable since the aircraft gas turbine manufacturers require that cast blades retain essentially their temperature properties in cast blades employed in the aircraft gas turbine.

One nickel-base alloy which has received wide acceptance in the aircraft and automotive gas turbine fields is the-alloy manufactured under the specification AMS 5391, which alloy nominally contains about 12.5%'

chromium, about 4.2% molybdenum, about 2.2% colurnbiurn, about 6.1% aluminum, about 0.8% titanium, about 0.12% carbon, about 0.012% boron, about 0.01% zirconium and and the balance essentially nickel. This alloy is characterized by excellent castability, by a high resistance to oxidation and thermal fatigue and by good structural stability when exposed to the effects of temperature and stress for extended periods of time. 'Recently, the aircraft gas turbine industry has been requiring that an alloy employed in gas turbine blades pass an acceptance test of 23 hours life at 1800 F. and 29,000

pounds per square inch (p.s.i.). Theaforementioned alloy produced under specification AMS 5391 has a life to rupture at 1800 F. and 29,000 p.s.i. of only about 10 hours. In addition, the aforementioned alloy possesses original ductility for long periods of time. In this connection, it can be pointed out that the expected time in of 2,500 hours.

A new alloy composition for use in cast'aircraft gas turbine blades and for other high temperature service has now been discovered which has improved stress rupture life together with excellent castability, good resistance to oxidation and sulfidation, and improved structural stability when exposed to the deleterious effects of temperature and stress for extended periods of time.

It is an object of the present invention to provide a new. nickel-base alloy suitable for use in the form of castings.

It is a further object of the invention to provide cast articles made of a new nickel-base alloy which have greatly improved stress rupture properties.

- A further object of the invention is to provide a new cast nickel-base alloy having high stress rupture properties together with excellent structural stability.

It is another object of the invention to provide a new.

cast nickel-base alloy having good ductility over the wide temperature range up to about 1900 F.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing which depicts a Larson-Miller diagram for the alloy provided in accord ance with the present invention.

Broadly stated, the present invention comprises a nickelbase alloy having high stress rupture properties and improved structural stability when produced in the vacuum melted and vacuum cast form which contains about 4% to about 11% chromium, about 0.5% to 3% columbium, about 0.5% to 4% tantalum, about 2% to 6% molybdenum, about 0.5 to 4% tungsten, about 5% to 8% aluminum, upto about 1.25% titanium, up to about 0.18%

- talum, about 3%to about-5% molybdenum,--about 1% to about 3% tungsten, about 6% to about 7% aluminum, up to about 1.1% titanium, up to about 0.15% carbon, with the titanium content and the carbon content being so related that when the carbon content does not exceed about 0.1% the titanium content does not exceed about 0.6%, about 0.005% to 0.02% boron, about 0.05% to 0.15% zirconium, and the balance essentially nickel.

It is important that the alloys provided in accordance with the invention be produced using the purest materials commensurate with reasonable cost. Thus, the contents of subversive impurities such as lead, bismuth, telluriurn, sulfur, oxygen, nitrogen, hydrogen, arsenic, antimony, tin

and thallium should be as low as possible. Cobalt and iron may be present in impurity amounts, e.g., up to about 1% of each, as these elements decrease the ability of the alloy to resist microstructural changes after long exposure to elevated temperature. Silicon and mangagese are detrishould not exceed about 4% as otherwise the density of the alloy is appreciably increased with deleterious effects on the strength-weight ratio. In dynamic machinery such as a gas turbine, this factor is quite important. Castings produced from the alloy No. 4 composition were subjected mental elements and should not be present in amounts ex- 5 to oxidation tests and sulfidation tests. Oxidation tests ceeding about 0.1% of each. comprised cyclic exposure in air, to a heating for 16 hours The compositions set forth hereinbefore are maintained at 1900 F., and to a cooling for 8 hours. After 208 within the ranges given in order to obtain the high comhours in the cyclic test, the weight loss for the alloy of bination of strength properties and other properties char- 10 the invention was only 0.005%. The sulfidation test comacterizing the same as it is found that if any of the eleprised exposure to a molten mixture of 90% sodium sul ments is employed in greater or lesser amounts than those fate and 10% sodium chloride for one hour at 1700 F. specified, the properties of the alloy are detrimentally No weight loss resulted. effected. It will be appreciated that the accompanying draw- The following table includes the compositions of five ing demonstrates the means whereby the rupture life alloys in accordance with the invention: for the alloy of the invention may be ascertained under TABLE I Per- Per- Per- Per- Per- Per- Per- Per- Per Pcr- Per- Alloy No cent cent cent cent cent cent cent cent cent cent cent Cr Mo W Cb Ta Al Ti 0 B Zr Ni 4 2 1 2 0.5 0 0.04 0.02 0.1 Bal. 3.6 2.07 0.7 2.77 0.42 0.1 0.04 0.02 0.042 Bal. 4 2 1 2 6.5 1 0.15 0.02 0.1 Bal. 3.9 2 0.90 1.97 6.58 0.94 0.12 0.013 0.057 Hal. 4 2 1 1 6.5 1 0.12 0.02 0.1 Bal.

The foregoing alloys were produced by vacuum melting any condition of load or temperature within the ambit and vacuum casting into various forms, including cast-to- 90 of the chart depicted. size test bars having gage sections about 0.250 inch in 0 Castings produced from the alloy provided in accorddiameter and about one inch long. The stress rupture ance with the invention may be employed not only in properties of the castings in the as-cast condition were aircraft and automotive gas turbine blades but also in determined under a number of conditions with the folextrusion dies, hot forging dies, and turbine rotors. The lowing results: castings so produced may vary widely in section up to TABLE H about 12 inches in diameter and good properties such as illustrated hereinbefore are obtained even in such Tempera- Life to Elongation, heavy Section Castings- Y N0 f .P- 3511151116, Percent Castings may be produced from the alloy provided ours in accordance with the invention by a process comprising investment casting, static casting, etc. 1 i288 231888 331 3:? Although the present invention has been described in 2 1 igconjunction with preferred embodiments, it is to be 11650 301000 5g() 1.; understood that modifications and variations may be 1 588 338% 2g? resorted to without departing from the spirit and scope 11800 201000 378:8 11,6 of the invention as those skilled in the art will readily 1,900 18,000 understand. Such modifications and variations are con- 1,900 15,000 160.6 8.9 3 1,400 85,000 213 4, sidered to be within the purview and scope of the iniggg 38 888 25 2 vention and appended claims. 4 1,400 90,000 258.7 4.0 I clalmr itggg 331888 9 g; 1. A nickel-base alloy having a high combination of 11800 201000 337' 4:4 mechanical properties together with structural stability 5 1,800 29,000 351 when subjected to the combined effects of temperature 1,800 29, 000 42. 7 10. 0 1,800 29,000 60.6 10.0 and stress for extended time periods in cast form and consisting essentially of about 4% to about 11% chromium, about 0.5% to 3% columbium, about 0.5% to In addltion, the tensile properties of cast-to-size test bars 4% tantalum about 2% to 6% molybdenum, about at room temperature were determined with the following 05% to 4% tungsten, about 5% to 8% aluminum, up results: to about 1.25% titanium, up to about 0.18% carbon, TABLE III with the titanium and carbon contents being so related that when the carbon content does not exceed about Yield Tensile Elongation, Reduction 0.10% the titanium content does not exceed about 0.6%, gig? 53 5 Pemem i fiffig about 0.005% to 0.03% boron, about 0.01% to 0.2%

Zirconium, and the balance essentially nickel. 110,000 136,000 15 16 2. A nickel-base alloy having a high combination of igfi gg ggiigg 2-3 13-2 mechanical properties together with structural stability when subjected to the combined effects of temperature and stress for extended time periods in cast form and It is found that turbine blade castings produced under consisting es n i lly of about 9% to 11% Chromium, commercial conditions using conventional investment castabout 0.5% to 1.5% columbium, about 1% to 3% ing procedures resulted in castings which passed all corntantalum, about 3% to about 5% molybdenum, about mercial tests for soundness, including the X-ray inspection 1% to about 3% tungsten, about 6% to about 7% and dye penetrant inspection. It is found that the denaluminum, p to about titanium, p 0 about sity of the alloy is about 0.290 pound per cubic inch (8.04 0.15% carbon, with the titanium content and the cargrams per cubic centimeter). In this connection, it will bon content being so related that when the carbon conbe appreciated that the tungsten content of the alloy tent does not exceed about 0.1% the titanium content 5 does not exceed about 06%, about 0.005% to 0.02% boron, about 0.05%, to 0.15% zirconium, and the balance essentially nickel.

3. A nickel-base alloy having a high combination of mechanic-a1 properties together with structural stability when subjected to the combined effects of temperature and stress for extended time periods in cast form and consisting essentially of about 10% chromium, about 4% molybdenum, about 2% tungsten, about 1% columbium, about 2% tantalum, about 6.5% aluminum, about 0.04% carbon, about 0.02% boron, about 0.1% zirconium, and the balance essentially nickel.

4. A nickel-base alloy having a high combination of mechanical properties together with structural stability when subjected to the combined efiects of temperature and stress for extended time periods in cast form and consisting essentially of about 10% chromium, about 4% molybdenum, about 2% tungsten, about 1% co1um bium, about 2% tantalum, about 6.5% aluminum, about 1% titanium, about 0.15 carbon, about 0.02% boron,

about 0.1% zirconium, and the balance essentially nickel.

References Cited by the Examiner UNITED STATES PATENTS 2,920,956 1/1960 Nisbet et al. 75171 3,085,005 4/1963 Michael et al. 75171 3,228,095 1/1966 Bird et a1. 75171 DAVID L. RECK, Primary Examiner.

R. O. DEAN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,301 ,670 January 31, 1967 Clarence G. Bieber It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letter: Patent should read as corrected below.

Column 1, line 60, strike out "and", second occurrence; column 2, line 49, for "0.5" read 0.5% line 50, for upto" read up to column 3, TABLE I, first column, line 1 to 5 thereof, strike out the leaders and insert instead the vnurgl bers "l", "2", "3, "4" and "S" in descending vertical or er Signed and sealed this 17th day of October 1967.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

1. A NICKEL-BASE ALLOY HAVING A HIGH COMBINATION OF MECHANICAL PROPERTIES TOGETHER WITH STRUCTURAL STABILITY WHEN SUBJECTED TO THE COMBINED EFFECTS OF TEMPERATURE AND STRESS FOR EXTENDED TIME PERIODS IN CAST FORM AND CONSISTING ESSENTIALLY OF ABOUT 4% TO ABOUT 11% CHROMIUM, ABOUT 0.5% TO 3% COLUMBIUM, ABOUT 0.5% TO 4% TANTALUM, ABOUT 2% TO 6% MOLYBDENUM, ABOUT 0.5% TO 4% TUNGSTEN, ABOUT 5% TO 8% SLUMIUM, UP TO ABOUT 1.25% TITANIUM, UP TO ABOUT 0.18% CARBON, WITH THE TITANIUM AND CARBON CONTENTS BEING SO RELATED THAT WHEN THE CARBON CONTENT DOES NOT EXCEED ABOUT 0.10% THE TITANIUM CONTENT DOES NOT EXCEED ABOUT 0.6%, ABOUT 0.005% TO 0.03% BORON, ABOUT 0.01% TO 0.2% ZIRCONIUM AND THE BALANCE ESSENTIALLY NICKEL. 